R53 engine squeal

[Aussie R53]

Hi everyone, I'm hoping someone on here might have an idea of what could be causing an issue with my R53.

So after giving the old beast a going over and replacing every oil seal in then engine, fitting a catch can, replacing all of the engine and gearbox mounts, servicing the supercharger and replacing some coolant hoses and water pump, the car has developed a hideous squeal after about 10 seconds in of idle and then continues for about 3-5 seconds after the engine is shut off and the crank stops spinning.

I thought it may have been the power steering at first so I disconnected the electrical connections but the squeal was still there. It almost sounds like its coming from around the front right of the motor above the oil filter.

It sounds like a bearing noise but has me puzzled as it continues for the short period after shutdown. Possibly a weird vacuum leak? Does any one have ideas or experience with such a noise? Thanks everyone.

Here is a video of the noise.
https://youtu.be/3FWtyb6iKP0

[MINICooperS1966]

One vote here for a bearing failure on any item driven by the serpentine belt . . . take your pick.